Ideas for a problem that causes battery to drain after a rain storm?

Hey Yall,

My gf has been facing an issue for a very long time with her car's battery draining, and her dad keeps insisting to get a new battery/trickle charge the battery every single time for many years now. I've noticed that it typically happens after a rain/snow storm and that some of the wires leading to the negative end are exposed. I am no mechanic and all I really know is how to remove the battery to trickle charge and jump start it. I feel like there is a preventive solution that can happen that isnt buying a new battery/taking the battery out every time there is a rain storm, I just have no idea what it may be.

If anyone has any ideas I would be very open to them to present as a possible issue that can be solved. Her dad takes the car to his friend whos a mechanic and every single time he says that the car works fine, just the battery being the issue, but I feel like the repeating nature of it suggests otherwise and her dad is just take his friend at his word.

Thanks again for the ideas and for reading through!

P.S. Not sure it helps but the car is a 2010 Hyundai Elantra.